Context : A group of trans-Neptunian objects ( TNO ) are dynamically related to the dwarf planet 136108 Haumea .
Ten of them show strong indications of water ice on their surfaces , are assumed to have resulted from a collision , and are accepted as the only known TNO collisional family .
Nineteen other dynamically similar objects lack water ice absorptions and are hypothesized to be dynamical interlopers .

Aims : We have made observations to determine sizes and geometric albedos of six of the accepted Haumea family members and one dynamical interloper .
Ten other dynamical interlopers have been measured by previous works .
We compare the individual and statistical properties of the family members and interlopers , examining the size and albedo distributions of both groups .
We also examine implications for the total mass of the family and their ejection velocities .

Methods : We use far-infrared space-based telescopes to observe the target TNOs near their thermal peak and combine these data with optical magnitudes to derive sizes and albedos using radiometric techniques .
Using measured and inferred sizes together with ejection velocities we determine the power-law slope of ejection velocity as a function of effective diameter .

Results : The detected Haumea family members have a diversity of geometric albedos \sim 0.3-0.8 , which are higher than geometric albedos of dynamically similar objects without water ice .
The median geometric albedo for accepted family members is p _ { V } = 0.48 _ { -0.18 } ^ { +0.28 } , compared to 0.08 _ { -0.05 } ^ { +0.07 } for the dynamical interlopers .
In the size range D = 175 - 300 km , the slope of the cumulative size distribution is q =3.2 _ { -0.4 } ^ { +0.7 } for accepted family members , steeper than the q =2.0 \pm 0.6 slope for the dynamical interlopers with D < 500 km .
The total mass of Haumea ’ s moons and family members is 2.4 % of Haumea ’ s mass .
The ejection velocities required to emplace them on their current orbits show a dependence on diameter , with a power-law slope of 0.21-0.50 .

Conclusions :